An organic electroluminescence device (hereinafter, occasionally abbreviated as an organic EL device) using an organic substance is highly expected to be used as a device for a full color display having a large area in a form of a low-cost solid-emitting device, so that the organic electroluminescence device has been variously developed.
A typical organic EL device is configured to include a pair of opposing electrodes and an emitting layer interposed between the pair of opposing electrodes. When an electric field is applied between both of the electrodes, electrons are injected from the cathode and holes are injected from the anode. The injected electrons and holes are recombined in the emitting layer to form excitons. When the excited state is returned to the ground state, energy is radiated as light. The organic EL device emits light according to this principle.
A typical organic EL device requires a drive voltage higher than that for an inorganic light-emitting diode. Properties of the typical organic EL device are also significantly deteriorated, so that the typical organic EL device is in no practical use. Although organic EL devices have been gradually improved recently, further lowering of the voltage is demanded.
Patent Literature 1 (U.S. Pat. No. 5,645,948) discloses an organic EL device including a benzazole compound. Moreover, Patent Literature 2 (JP-A-2010-34548) and Patent Literature 3 (International Publication No. 2006/128800) also disclose organic EL devices.
However, demanded is an organic EL device driven by a voltage further lower than that of the organic EL device using a nitrogen-containing heterocyclic derivative disclosed in Patent Literature 1.